This invention relates to a device for automatically switching a plurality of outlet ports from which pressurized fluid is discharged.
To be more specific, this invention relates to an automatic pressurized fluid switching device for performing a switching operation using the pressure of pressurized fluid in itself without using electrical elements.
As a conventional technique for automatically switching discharge of high pressure fluid such as oil and air from outlet ports, there has been known a device using electrical elements such as an electromagnetic valve and so on (cf. Japanese Patent Publication SHO 46-20414(B)). However, the conventional device entails problem such as lack of versatility, since the electrical elements have restrictions on applicability.
There has been known another device incorporating various mechanical valve systems which operate with the pressure of pressurized fluid. However, this conventional device has a possibility that a smooth switching operation cannot securely be effected when being again operated after stopping at an intermediate point of the switching action. To solve the problem noted above, the conventional device is provided with a valve mechanism or a mechanism for producing an expansion force by the pressurized fluid so as to smoothly carry out infallibly the switching operation with the expansion force of the pressurized fluid, resulting in complexity of the overall structure.
The present invention was made in the light of the foregoing problems, and has an object to provide an automatic pressurized fluid switching device having an excellent switching performance without using an electrical element so as not to be complicated in structure.
As set forth in claim 1, a solution of the technical problems as described above is to provide an automatic pressurized fluid switching device comprising an inlet port for introducing pressurized fluid, a plurality of outlet ports for discharging the pressurized fluid, a switching valve disposed between the inlet port and the outlet ports for switching over the outlet ports, a pilot valve for piloting the switching operation of the switching valve, and a reaction member for controlling the pilot action of the pilot valve in response to the pressure of the pressurized fluid introduced, which is characterized in that the pilot valve is provided with a first pilot unit in which the pilot action of the pilot valve is controlled only by the reaction member, and a second pilot unit in which the pilot action of the pilot valve is controlled by the reaction member in its initial and final stages and directly by the pressurized fluid in its middle stage.
According to the solution of the technical problems described above, two lineages of the pilot action of the pilot valve for piloting the switching action of the switching valve can be constituted.
Thus, the lineages are formed of the pilot action controlled only by the reaction member in the first pilot unit and the pilot action controlled by both of the reaction member and the fluid in the second pilot unit. The pilot action in the second pilot unit is controlled by the reaction member in the initial and final stages and by the pressurized fluid in the middle stage. In other words, the pilot action in the second pilot unit in the middle stage is left free from the controlling of the reaction member.
Consequently, the pilot action in the second pilot unit in the middle stage can be securely effected even when the pressurized fluid introduced thereinto is little at the time of being again operated after stopping at the intermediate point of the switching action. Thus, smooth switching action can be performed securely. There is however no call for providing a mechanism for producing expansive power on the pressurized fluid.
As a result, a simple automatic pressurized fluid switching device having excellent switching performance can be fulfilled without using electrical elements.
The automatic pressurized fluid switching device provided as another solution of the aforesaid technical problems as set forth in claim 2 is featured in that the reaction member in the structure set forth in claim 1 comprises an operating piston mounted in a reciprocative sidable state within an operating chamber formed between the inlet port and the outlet port, each of the first pilot units of the pilot valve comprises a push rod having a front portion which protrudes into the operating chamber to come in touch with the operating piston, a flange formed in the middle of the push rod, and a pilot piston mounted at the rear portion to receive the pressure of the pressurized fluid, and each of the second pilot units of the pilot valve is formed of a sleeve fitted sidably in the rear portion side of the push rod, wherein the sleeve is shorter than the length from the flange of the push rod to the rear end thereof so as to control the pressure of the pressurized fluid applied to the switching valve.
According to this solution, the reaction member can be formed of the operating piston of a reciprocating type, which is simplest in structure. Thus, the automatic pressurized fluid switching device can be made simple in structure. Furthermore, the first and second pilot units of the pilot valve are arranged coaxially, so that they can be assembled compact. Consequently, the structure of the device can be made more simple.
As set forth in claim 3, the other solution of the technical problems described above is featured in that the reaction member in the structure set forth in claim 1 comprises an operating piston mounted in a reciprocative sidable state within an operating chamber formed between the inlet port and the outlet port, each of the first pilot units of the pilot valve comprises a push rod having a front portion which protrudes into the operating chamber to come in touch with the operating piston, a flange formed in the middle of the push rod, and a pilot piston mounted at the rear portion to receive the pressure of the pressurized fluid, and each of the second pilot units of the pilot valve is formed of a sleeve fitted sidably in the rear portion side of the push rod, wherein the sleeve is slightly shorter than the length from the vicinity of the front portion to the rear portion of the push rod of the first pilot unit so as to control the pressure of the pressurized fluid applied to the switching valve.
According to this solution, the reaction member can be formed of the operating piston of a reciprocating type, which is simplest in structure. Thus, the automatic pressurized fluid switching device can be made simple in structure. Furthermore, the first and second pilot units of the pilot valve are arranged coaxially within a double structure, so that they can be assembled compact. Consequently, the structure of the device can be made more simple.